Electric temperature and burglar alarm system



Nov. 10, 1936. R. M. HOPKINS ET AL ELECTRIC TEMPERATURE AND BURGLAR ALARM SYSTEM Filed May 5, 1931 3 Sheets-Sheet l ATTOR-NEY Nov. 10, 1936. R. M. HOPKINS ET AL ELECTRIC TEMPERATURE AND BURGLAR ALARM SYSTEM Filed May 5, 1931 5 Sheets-Sheet 2 Nov. 10, 1936. R. M. HOPKINS ET AL ELECTRIC TEMPERATURE AND BURGLAR ALARM SYSTEM Filed May 5, 1931 3 Sheets-Sheet 5 In menions Rickard/EJ70 011 inpr flerfieilmlqforal BY @M/Wq ATTORNEY Patented Nov. 10, 1936 UNITED STATES PATENT. OFFICE ELECTRIC TEMPERATURE AND BURGLAB ALARM Richard M. Hopkins,

Herbert M. Iaford, New York, -N.

to American District York, N. Y., a corporation Telegraph Company, New

of New Jersey Application May 5, 1931, Serial No. 535,191 6 Claims. (Cl. 177-314) The present invention relates to an electrical alarm system, and has for its primary purpose the provision of a room, or vault alarm having the dual function of providing said room or vault with alarm means against fire, or burglarizing, to give visible or audible warning in the event of fire or unauthorized entry, or both.

The device comprehends the use of the Wheatstone bridge principle, so modified as to create an accurate, alarm initiating means, of great sensitivity and having therein a fixed, predetermined set of resistances, single or plural, in each leg of the bridge, so that normally at all times except at the moment of functioning by the noted disturbances, the bridge is in electrical balance in all legs thereof, and therefore is normally quiescent.

The numbers of resistances or pairs of resistances in each leg of the bridge may be unequal or equal, and may be multiplied to suit the number of required stations installed in a zone to be protered, as will be more specifically set out in detail, hereinafter.

Further, the single or paired resistances are so arranged and selected that each element of any element or pair, in any leg, are of unlike temperature coefiicients. This will be better understood by stating as will hereinafter be described, relative to the drawings, that any one element of any leg or pair of resistances may be of a carbon filament, or wire, which has a temperature coeflicient of minus .0005 ohms per degree centigrade, while the other element of such leg or pair may be a tungsten filament or wire which has a temperature coefiicient of plus .0089 ohms per degree centigrade.

The differences above noted, therefore, become the means whereby the associated alarm system becomes operative, upon sudden local temperature changes within the zone or room. These sudden, local temperature changes, as will be later pointed out, cause a state of unbalance in the Wheatstone system and cause the alarm to function.

Gradual room temperature changes affecting all of the sensitive elements of the bridge, either of depressed or raised room temperature, will not cause the system to initiate an alarm, thus the 50 device will automatically compensate itself for varying general or average room temperatures, plus or minus, but at all times sensitive to sudden local temperature changes or rises, from any maximum or minimum self-compensated temperature point or condition.

It will be obvious from the foregoing and as the description proceeds, that variations may be made in the material of the paired resistance elements, their mode of distribution within a room, or the form of alarm means may be varied, from the herein described device, or the scope of the appended claims, without departing from the principles of the system as herein outlined.

In the drawings, diagrams are entirely resorted to throughout, as the best and simplest method of outlining the device as herein dis closed, and, further, all like parts and elements have the same indices, for brevity, convenience and easier understanding.

Fig. 1 shows a simple form of the device and diagrammatically outlines a Wheatstone bridge modified to illustrate the main principles of the present invention;

Fig. 2 shows a translating means including an alarm and an alarm relay in connection with the alarm initiating galvanometer of such Wheatstone system;

Fig. 3 is a modified system showing a (one) set of control filaments in each leg of the bridge;

Fig. 4 is a sectional diagrammatic plan view of a room with the bridge system of Fig. 3 distributed at different points in such room with a distant bridge initiated alarm relay circuit con-' nected thereto;

Fig. 5 is a further modified bridge alarm system showing plural (two) sets of pairs of control filaments in each'leg of the bridge; I

Fig. 6 shows a diagrammatic plan view of the protective distribution or location of such pairs of filaments in a room;

Fig. 7 is a still further modified bridge system showing a greater plurality of (three) sets of filaent pairs in each leg of a bridge circuit;

Fig. 8 is a diagrammatic plan layout of one form of protective room disposition of the bridge layout of Fig. 7; and

Fig. 9 is a fragmentary elevational view of the door or entry to the room of Fig. 4, showing a relative location of a pair of the protective filaments of the bridge layout of Fig. 3 in room door protecting position.

As showing how this is accomplished, attention is called to Figs. 1, 2 and 4 in which the normally balanced Wheatstone bridge ABCD is shown. Each leg of any two adjacent legs C, D (or A, B, or A, C or B, D or of all of them) may comprise an exposed element c (cl, c2, 03 or cl) such as carbon having a negative temperature coefllcient and an exposed element t (tl, t2, t3 or t4) such as tungsten having a positive temperature coefficient. A positive element (for instance ti) or each leg (as C) is closely adiacently associated with a negative element (as 02) of the adjacent leg (as D) to form a station set up, as shown in Fig. 4 by the set-ups ti, citl, t3c4 and cltl. Other combinations such as set-ups cit2, cltl, c3t4 and clti or any number of them would, be good. It is only necessary that the elements of difi'erent sign be in adjacent legs.

The station set-ups may be disposed in the upper part -V of the room It at widely separated points to form stations, one of them being near the door V. The alarm 23 is operated by said bridge when the bridge becomes unbalanced. Corresponding elements as ti, t2 or t2, t3 of each pair of adjacent legs may be substantially equal in length, diameter and radiating coefficient, whereby the bridge remains balanced whenever the temperatures at the stations remain equal, even should the temperatures at all stations change equally and suddenly. However change of temperature at one station as cit! relative to another cit! causes a decrease of resistance in one of said adjacent legs and an increase in the other, whereby the bridge becomes doubly unbalanced and greatly unbalanced on a slight difference in temperature, and the alarm operated.

Fig. 1 shows a broader aspect of the invention, showing that only one resistance need be in each leg. Thus the bridge of Fig. 1 may provide two stations, as by bringing resistances, ci, 1:2 together as in the upper right of Fig. 4, and bringing together resistances 03 as in the lower right of Fig. 4.

So long as the room temperature is relatively uniform at the stations, the bridge remains balanced; but if the temperature at set-up cl, t2 becomes not the same as at set-up c3, t4, the bridge becomes unbalanced, and the alarm operates.

As a continuation oi the system herein disclosed there is shown in Fig. 2, an alarm circuit and relay, for giving warning of either entry, or undesired temperature changes within the protected zone. To this end the galvanometer G and the two contact switches s are again shown, as in Fig. 1, with the connections E, F, indicated, but with a relay coil operating wiring circuit 7, 8, 9, 10, one end of which as at 1 is connected to the switch s the other end of said circuit, as Ill, being connected to the galvanometer needle. A current source ii is connected into this circuit, and upon operation of the galvanometer needle to close upon switch s, the coil i2 is actuated to draw armature i 6 upon pivoted switch lever i3, upward upon its pivot i4, and thus close contacts i1i8 thereby actuating alarm circuit iii-20, 2i, in which is mounted and connected an alarm 23 and a source of current supply 22. The lever i3 is normally stressed by a pin held spring i5 to remain open until the coil i2 actuates it. This alarm relay means is also shown in Fig. 4 with the same indices as above described.

Thus under normal conditions of the bridge circuit the alarm relay gives no alarm, but upon any change of balance in the bridge circuit the alarm is caused to give warning.

To accomplish this, reference may be had to Fig. 1. In this figure, in leg A, is shown a resistance element 03 in heavy lines to represent a carbon filament. In leg B is shown a resistance element ii, in light lines to represent a tungsten filament. In leg C is shown a carbon filament ci in heavy lines, while in leg D is shown a resistance element t2 in light lines. This heavy and light lining to represent carbon and tungsten eleis thereby ments in the various legs of all Wheatstone bridge diagrams shown herein is adhered to throughout, and the indices c and t to indicate carbon or tungsten elements is also utilized where a plurality of such elements are utilized in each leg is also adhered to with changed exponents, to identify each added resistance element of a leg group.

Obviously, with an arrangement as set out in Fig. 1, sudden local temperature changes affecting any of the filaments c or t in any leg cause the galvanometer G to deflect its needle and cause an alarm. Normal rises or depressions of temperature affecting all of the c and t elements, such as would normally occur in a closed room or protected zone, will not disturb the equilibrium of the bridge circuit.

As a better illustration of the idea, Fig. 3 discloses a bridge circuit identified and exactly like that as described for Fig. 1, with the exception that each leg of the bridge A, B, C, D, has an added resistance element therein of opposite characteristics. Whereas, in Fig. 1, legs A, B, C, D, have elements 03, t4, ci and t2 respectively, these same legs in Fig. 3, have elements c3+t3, tH-cl, tl+ci, and c2+t2 respectively.

Thus in Fig. 3 each leg has a balancing pair of thermally sensitive elements comprising a carbon and tungsten pair in each leg.

The purpose of this latter structure, in one form of installation is exemplified in Fig. 4 in which there is disclosed a diagrammatic plan of a room or zone to be protected against sudden temperature disturbances, such as a fire within, or the entry of an individual who may move about said room thereafter. Thus, the confines of the zone are shown by the walls R, and in which is a door or point of entry V, and in which is located a Wheatstone bridge circuit and a preferably external and distant alarm system. The

indices and functions of the parts of the various elements are like those as previously described, and it is thought need no further detailed identification or explanation.

Thus Fig. 4 shows that by reason oi. there being two c and t elements in each leg of the bridge, it is possible to control by proper distribution through the protected zone, a four station set up, as shown in each of the four comers of Fig. 4. As thus shown, each station set up comprises a c and t couple of each leg of the bridge system, as will be noted by the indices thereon.

Obviously, the location of the c and t couples in Fig. 4 are disposed at room distances from one another, to such an extent that general temperature conditions within the room keep the bridge system in a state of automatically compensated balance, and therefore in non-alarm condition. Such changes as may occur are gradual and affeet all of the c and t elements simultaneously.

In Figs. 4 and 9, a pair of elements t3 and at are shown as being adjacent a door V. When normal conditions prevail within the zone or room R, any tendency to disturb'those normal conditions such as opening the door V or a window or breaking through the wall of the room cause a disturbance of the static conditions of the room atmosphere and thus create a sudden change therein.

In Fig. 9 there is shown a dotted line X which can indicate a line of demarcation between stratas of room atmospheric temperatures, the upper strata Y above line X being a little warmer than the strata 3 below line X. Undisturbed, the temperature of these stratas remain quite constant. Entry by opening the door causes admixtureoithesequiescentstratasand ailect door guarding couple, for instance, t8 and cl. cause a state oi. unbalance in the bridge circuit and set oi! the alarm.

Further, it has been found that bodily movement or an individual, around the room cause air disturbances and temperature changes and thereby cause an alarm to be initiated. Even in rooms, not closed from otherrooms, the passing therethrough oi an individual disturbs the normal equipoise or the bridge system and causes an alarm to be initiated.

A sudden increase in heat in the protected zone B will also affect the balance of the bridge circuit from whatever cause, though heat changes of a gradual nature from radiators or other room heating sources antomatically cause the bridge system to compensate itself and thus keep all legs 0! the system in balance.

Satisfactory results are obtained ii. the tungsten element is about two thousandths of an inch in diameter with resistance or 60 ohms at 22 (7., and the carbon element is about four thousandths of an inch in diameter with a resistance of 120 ohms at 22 C. A current flow through the battery of three tenths of an ampere renders the elements operatively sensitive to motion or disturbance within a radius of 10 to 12 feet. A current flow of four tenths amperes renders the system much more sensitive than required.

It is understood however that the invention is not limited to the particular designs and specifications herein indicated.

In order to increase the number oi! stations in any installation it is only necessary to provide additional 0 and t elements in each leg, this being illustrated fully in Figs. 5and 7, the zone distribution being shown in Figs. 6 and 8 respectively. Thus in Fig. 5 the sets of c and t elements as used in Fig. 6 may be outlined as follows:

Set #I, tl, c2, t4, 03.

Set #2, cl, t2, cl, t3.

Thus, the arrangement set out for Figs. 5 and 6 show arrangements of couples in four sets of control elements of four elements each. More or less may be used.

Again in Figs. '7 and 8 there are set forth a six element group for each leg or the bridge, Fig. 8 showing six sets of station distribution 01 four elements each. It is thought that, by reason of the explanation set out for the preceding figures that a detailed outline of the set distribution of Figs. '7 and 8 are unnecessary.

It is obvious, therefore, that owing to the spaced distribution, in a protected zone, of the c and t elements as hereinbeiore outlined, that we have provided a novel and eillcient alarm system, self compensating, under normal temperature change conditions, against a state of unbalance, but extremely sensitive to sudden local temperature changes from any cause to cause a state of unbalance and thereby initiate a warning thereof.

It is obvious, also, that other groupings of the c and t elements may be utilized, in a greater number of distributed control stations than herein outlined, and that other sensitive elements having divergent temperature co-efllcients may be substituted for the carbon and tungsten resistance elements herein outlined.

Having thus described the invention, what is claimed is: I

1. In combination, a normally balanced Wheatstone bridge of which each or two adjacent legs comprises an element having a negative temperature coeiilcient and an element having a positive temperature coeilicient; a positive element of one leg being closely adiacently associated with a negative element of the adjacent leg andremote from the other elements. 1

2. In combination, a normally balanced Wheatstone bridge of which each of two adjacent legs comprises an element having a negative temperature coenlcient and an element havinga positive temperature coefllcient; a positive element of each leg being adjacently associated with a negative element of the adiacent leg to form a station set-up; a translating means controlled by the balance of said bridge; corresponding elements or the set-ups being substantially equal in resistance and radiating eflect, whereby the bridge remains balanced it the temperatures at the stations remain equal.

3. In combination, a normally balanced system of which each or two balancing parts comprises an element having a negative temperature coefllcient and an element having a positive temperature coefllcient; a positive element of each part being adiacently associated with a negative element of the other part to form a station'setup; the set-ups being disposed at widely separated points; a translating means controlled by the balance of the system; corresponding elements of the set-ups being substantially equal in resistance and radiating eflect, whereby the sys-v tem remains balanced ii the temperatures at the stations remain equal; change 01. temperature at one station relative to the other causing a decrease of resistance in one of said parts and an increase in the other part at the same station, whereby the system becomes considerably unbalanced on a slight diiference in temperature.

4. In combination, a normally balanced Wheatstone bridge of which two adjacent legs each comprise an element having a. negative temperature coeillcient and an element-having a positive temperature coeillcient; a positive element of each leg being adjacently associated with a negative element of the adjacent leg to form a station set-up; a room having a door; the set-ups being disposed in substantially the same level of said room at widely separated points, one of them being near the door; a translating means controlled by the balance 01' said bridge; corresponding elements of the set-ups being substantially equal in resistance and radiating effect, whereby the bridge remains balanced it the temperatures at the stations remain equal; change of temperature at one station relative to the other causing a decrease of resistance in one of said adjacent legs and an increase in the other of the same station, whereby the bridge becomes considerably unbalanced on a slight difference in temperature.

5. In combination, a normally balanced Wheatstone bridge of which each of two adjacent legs comprises an exposed element such as carbon having a negative temperature coeillcient and an exposed element such as tungsten having apositive temperature coefllcient; a positive element of each leg being closely adjacently associated with a negative element of the adjacent leg to form a station set up; a room having a door; the station set-ups being disposed in an upper level of said room at widely separated points to form stations, one of them being near the door; and an alarm set oil by said bridge when the bridge becomes unbalanced; correative temperature coemcient and an exposed element having a positive temperature coemcient; a positive element of each leg being closely ad- Jacently associated with a negative element of the adjacent leg; a translating means; means controlled by the bridge for controlling the translating means when the bridge is changed from balanced to unbalanced condition and vice versa; said exposed elements and the bridge being suificiently sensitive to a few degrees variation in temperature to control the translating means. RICHARD M. HOPKINS. HERBERT M. LAFORD. 

